Definition of Almagest in US English:



the Almagest
  • 1An influential treatise on astronomy written by the Greek astronomer and geographer Ptolemy in the second century AD.

    • ‘Menelaus's work formed the basis for Ptolemy's numerical solutions of spherical astronomy problems in the Almagest.’
    • ‘Finally, the translation of Ptolemy's Almagest furnished important astronomical material.’
    • ‘Ptolemy's Almagest was one of the works which Arabic scientists studied intently.’
    • ‘Ptolemy's Almagest was a complete theory, but it involved applying a different mathematical formula for the motion of each planet and therefore did not really represent an overall unifying system.’
    • ‘But once they had translated Ptolemy's Almagest, they developed astronomy so quickly that their mark is found at every step.’
    1. 1.1 (in the Middle Ages) any celebrated textbook on astrology and alchemy.


Late Middle English: from Old French almageste, based on Arabic, from al ‘the’ + Greek megistē ‘greatest (composition)’.